1. Field of Invention
The present invention relates to a fluid droplet discharge device in which the fluid tank is connected through a fluid supply path to the fluid droplet discharge head when the access cover of the fluid tank loading unit closes, and the fluid tank disconnects from the fluid supply path to the fluid droplet discharge head when the access cover of the fluid tank loading unit opens. More particularly, the present invention relates to a head cleaning control method for a fluid droplet discharge device enabling efficiently recovering nozzles of the fluid droplet discharge device that are become faulty when bubbles enter the fluid supply path.
2. Description of Related Art
An inkjet printer having an inkjet head that prints by discharging ink droplets from nozzles is a common type of fluid droplet discharge device having a fluid droplet discharge head that discharges fluid droplets from a nozzle. The discharge of fluid droplets from a nozzle of the fluid droplet discharge head in such a fluid droplet discharge device can become deficient or not possible. Using an inkjet printer by way of example, the nozzles of the inkjet head can become clogged by an increase in the viscosity of the ink or other fluid droplets left inside a nozzle, by the intrusion of bubbles, or by adherence of foreign matter to the nozzles, resulting in the nozzle becoming unable to discharge ink droplets. A nozzle may also become partially clogged, resulting in a deficient discharge condition in which ink droplets of sufficient volume cannot be discharged. If printing proceeds using an inkjet head having nozzles in either of these conditions (referred to below as defective nozzles), print quality may drop as a result of dropped (non-printing) dots, for example. To prevent this, the inkjet head is moved regularly or at a predetermined timing to a position outside the printing area for head cleaning, which may include flushing to discharge ink droplets from each of the nozzles or an ink suction operation to vacuum ink from the nozzles.
Japanese Unexamined Patent Appl. Pub. JP-A-2007-7960 discloses a printer with a nozzle check function for checking the nozzles and cleaning the print head (referred to below as simply “head cleaning”). When the power turns on, this printer performs nozzle check and head cleaning operations as part of the startup process. The nozzle check also detects the number of defective nozzles, executes a head cleaning operation appropriate to the number of defective nozzles if the number of defective nozzles is greater than or equal to a user-defined threshold value, and does not execute the head cleaning operation if the number of defective nozzles is less than the threshold value.
Ink cartridges are generally used as the ink supply source in an inkjet printer. An ink cartridge loading unit is located in the inkjet printer, and an access cover is opened to load the ink cartridge. An ink supply opening is formed in the ink cartridge, and an ink supply needle that can be inserted into the ink supply opening is positioned on the ink cartridge loading unit side. When the access cover closes, the ink supply opening of the ink cartridge is pushed toward the ink supply needle and the ink supply needle is inserted to the ink supply opening. This connects the ink cartridge to the ink supply path of the inkjet head, and enables supplying ink. When the cover then opens, the ink supply opening of the ink cartridge separates from the ink supply needle and the ink supply needle is thus exposed to air. So that air bubbles do not enter the ink supply path from the ink supply needle exposed to the air when the ink cartridge is replaced, for example, a valve positioned in the ink supply path is closed to close the ink supply path. Japanese Unexamined Patent Appl. Pub. JP-A-2007-106019 discloses an inkjet printer having this type of ink supply unit.
If the access cover to the ink cartridge loading unit is opened while flushing the nozzles to prevent the nozzles from clogging, the possibility of bubbles being drawn into the ink supply path from the ink supply needle now exposed to air is strong. Bubbles that get inside the ink supply path gradually advance inside the ink supply path toward the nozzles of the inkjet head in conjunction with the ink supply operation. If a bubble reaches a nozzle, the nozzle will be unable to discharge ink droplets or will discharge ink droplets with insufficient volume. This makes head cleaning, which vacuums a large volume of ink from the nozzles, necessary in order to remove bubbles that have entered from the ink supply needle end of the ink supply path.
The literature is silent, however, about measures for removing bubbles that enter the fluid supply path when flushing occurs with the access cover to the ink tank loading unit or ink cartridge loading unit open.